A cDNA library from the dengue type 4 virus 42s RNA (strain 814669) was constructed. Multiple overlapping DNA clones which represent the entire dengue genome were used to determine the complete nucleotide sequence. The genome contains 10,644 nucleotides with a single open reading frame that encodes a polyprotein of 3386 amino acids. Homology alignment of the dengue type viruses, indicated that the three structural proteins designated capsid(s), membrane (M), and envelope (E), are located at the N-terminus and nonstructural proteins in the order of NS1, NS2a, viral functional activities such as absorption to host cells, hemagglutination and reactivity with neutralizing antibodies. Amino and homology analysis indicates that there is a close sequence relationship among the envelope glycoproteins of different flaviviruses. The dengue NS1 nonstructural protein has been shown to be the soluble complement fixing antigen. Recent studies with YF or dengue virus have shown that NS1 induces immunity in mice against its respective virus infection. The use of NS1 nonstructural protein for immunization against dengue is especially attractive because the possibility of immune enhancement due to envelope glycoprotein- specific antibodies could be avoided.